海员机工英语期末考试试题
Ⅰ。Choose the best answer.（每题１分，共３０分）
1)In the engine room ,there is _______.
A.one main engine
B. one auxiliary engine
C. one generator
2)The workshop is ______.
A. in the engine room
B. on the bridge
C. on deck
3)There are many ______in the workshop.
A. engines
https://www.doczj.com/doc/6c14334372.html,thes
C. auxiliary machins
4)Usually ,each watch lasts _______hours.
A. four
B. six
C. eight
5)Each person is on watch _______a day .
A. once
B. twice
C. as he likes
6)All the members in the engine department should stand regular
watch _____the chief engineer.
A. beside
B. besides
C. except
7)There will be ______for us to do during the watch.
A. much work
B. a lot of works
C.some works
8)Our motormen _____the main engine and the auxiliary machines.
A. keep
B. take care of
C.is responsible for
9)We ____the main engine in the engine room .
A. keep
B. protect
C. maintain
10)Motormen do their work ____in the engine room,_____in the
workshop.
A. not ; but
B. neither ; nor
C. not only ; but also
11)The heavy oil systerm consists of _____ links.
A. one
B. too
C. three
12)The heavy oil is pumped to the ____ from the double bottom
tank .
A.slop tank
B. settling tank
C. service tank
13)As the purifier,the viscosity of the oil is generally to be adjusted
____ at Redwood No. 1.
A. 50sec.
B. 100sec.
C. 200sec.
14)You should drain off the heavy oil from the mixing tube____.
A. after the engine starting
B. after the engine stopping
C. before the engine starting
15)The heavy oil after setting and purification is purified_____the
purifier.
A.in
B. with
C. by
16)A four-stroke diesel engine includes _____.
A. exhaust stroke
B. compression stroke
C. A and B
17)_____ is a moving part.
A. Cylinder
B. Piston
C. Injector
18)The fresh air is sucked into the ____ at the first stroke.
A.piston
B. compressor
C.cylinder
19)Combustion completed,the hot gas exspands to force the piston
____.
A. forward
B. upwards
C. downwards
20)_____ is a fixed part .
A. Piston
B. Cylinder
C. Connecting rod
21)Please set the heavy oil to the _____temperature.
A. require
B. requires
C. required
22)It is recommended to _____the air of the cooler before using .
A.charge
B.heat
C. vent
23)Regulate the _____ to set the heavy oil to the required
temperature .
A. heater steam valve
B. heavy oil valve
C. fuel oil valve
24)The flash point of the heavy oil is _____ than the diesel oil .
A. high
B.higher
C. lower
25)_____ with hand , confirm whether the fuel pump body has been
heated.
A.touch
B. touching
C. touched
26)The ships are equipped _____ diesel engines.
A. with
B. by
C.for
27)The oil pressure is _____ the motor .
A. to low to turn
B. much low to turn
C. very low to turn
28)It ____ in hongkong during our last voyage .
A. is
B. was
C. are
29)Where _____ you have the last inspection .
A. did
B. do
C.does
30)It has ______ checked.
A.was
B. are
C. been
Ⅱ. Translate the following sentences in to chinese :（每题２分，共４０分）
31)The following figure is a short description of the four-stoke diesel
engine.
32)The air inlet velves is closed at the expression stroke.
33)Fule injection has taken place before combustion.
34)The cycle will be continuously repeated .
35)Has the imergency steering gear been checked ?
36)The inspection is carried out by port state .
37)Proceed to your muster stations immediately.
38)Board the lifeboat in order now.
39)Start the boat engine right now.
40)The fire extinguishing system
41)Start the emergency generater
42)Cut off the fule supply
43)Diesel engine
44)Bilge water
45)Emergency generator
46)Refrigerating plant
47)Exhaust gas boiler
48)How much oil can it treat every hour?
49)It can make 25 tons of fresh water a day.
50)It is on the first floor of the engine room.
Ⅲ. Translate the following phrases:（每题１分，共３０分）
⑴燃油驳运泵
⑵流量表
⑶储存柜
⑷溢流管
⑸燃油增压泵
⑹重油的净化与处理
⑺重油被泵到沉淀柜
⑻放掉沉淀柜中的水
⑼上止点
⑽下止点
⑾压缩冲程
⑿排气冲程
⒀排气阀
⒁燃油喷射装置
⒂二冲程船用柴油机
⒃迫使活塞向下运行
⒄上个月
⒅应急发电机
⒆水密门
⒇上一次的PSC检查
（21）小学
（22）中学
（23）英文说明书
（24）休息一会
（25）与轮机长联系
（26）烤鸭
（27）吃午饭
（28）在船上
（29）淡水冷却器
（30）海水泵
‖‖‘
紫云自治县2016—2017 学年度第一学期期末教学质量检测试卷（）13.—Do you often play football on the weekend? —________ 语五年级英 B. Yes, I do. C. No, I do. A. Yes, I am. 100分钟）100 分时间：（总分：）14. Where________the girl come from? （ A. are B. is C. does 题号一二三四五六七八九总分
（）15. ________nice camera it is! 分得A. What B. How C. What a 评卷人 三、根据所给场景，选择合适的句子。(10 分) 分）一、找出下列单词中与众不同的一项。（10 （）16.当你想知道今天是星期几时，应问：C. hot B. sweet （）1.A. tea A. What day is it today? B. What do you have? C. It's Monday? （B. bike C. lake ）17.当你想知道别人会做什么事时，应问：（）2.A. river A. What do you do? ）（3.A. park B. old C. young B. What can you do? C. What are you do? （）18.当你想知道别人最喜欢的食物是什么时，应问：（）4. A. flower C. mountain B. tree
A. What's your favorite food? B. What 's your best like food? C. Sunday 5. A. Friday B. dirty （）C. What's your favorite fruit? 20 分）二、单项选择。（（）19.当你想感谢对方时，应说：________is your English teacher? （6. ）—A. You are welcome. B. I see. C. Thank you! Miss Liu. —（）20.当你问别人想喝什么时，你应说： C. Who B. Which A. What A. What do you like? B. What would you like to drink? 7. I________ a student. （）C. What's your like? C. is B. are A. am 四、从 B 栏中选出 A 栏的最佳答语。（10 分）8.
精心整理 大学英语（一） 行政班级分级班级姓名学号 C. A measuring system. D. A control system. 2. A. Car prices. B. Car services.
C. The company’s business. D. The company’s culture. 3. A. It’s easy to do. B. It’s challenging. dialogue, there are some recorded questions. Both the conversations and questions will be spoken two times. Conversation 1
6. A. Breakfast. B. Dinner. C. A 5 dollar gift card. D. Bus service to the airport. 10. A. Make an appointment with her. B. Talk with her about a new order.
C. Send her an email about the shipment. D. Call her back when receiving the shipment. Directions: This part is to test your ability to construct grammatically correct sentences. It consists of 2 sections.
高级英语期末考试题型： Lexical work: Unit 1 1.ego: self, especially as contrast with another self or the world 2.disparity: a noticeable difference 3.prestigious: having prestige,i.e. general respect or admiration felt for someone or something, because they have high quality, social influence, success, etc. 4.allot: give as a share or set apart for a purpose 5.typify: be a typical example of, show all the most usual characteristics of something Unit 2 1.minute: very small 2.chartered: hired for use by a particular group or person 3.a standing order: a permanent request(for something by a customer) 4.extract: obtain by much effort 5.trinket: a small ornament(as a jewel or ring)of little value 6.flapping: swaying loosely, and making a noise, especially when moved by wind Unit 3 1.disorientation: confusion, loss of one's bearings 2.vistas: sweeping views 3.eerie: frightening because of strangeness or gloominess 4.tactile: relating to the sense of touch 5.redemption: forgiveness from the consequences of sin and evil which Christians believe was made possible by Jesus Christ's death on the cross赎罪. This is a religious term. 6.congealed: stiffened 7.wino: one who is chronically addicted to drinking wine Unit 4 1.constraints: restrictions, limitations 2.scale: a graded series/scheme/system of rank of order; something graded especially when used as a measure or rule尺度 3.norm: a standard, e.g. of behaviour or ability, that is regarded as average or generally accepted 4.formalities: a way of writing letters in accordance with accepted rules for official occasion 5.tautologous:unnecessarily repetitive, obvious 6.veribage:too many unnecessary words in speech or writing Unit 5 1.sulk: be silently bad-tempered 2.surreal: having a strange dreamlike unreal quality 3.malevolent: having a wish to harm others, showing intense ill will; here, strong, adverse, harmful 4.torrential:(rain)pouring down rapidly and in great quantities 5.radically: drastically: severely 6.accentuate: make(something)more noticeable Unit 6
濉溪县2019—2019 学年度第一学期期末考试 高二英语试卷 第一部分听力（共两节，满分20分） 第一节（共5小题；每小题1分，满分5分） 听下面5段对话。每段对话后有一个小题，从题中所给的A、B、C三个选项中选出最佳选项，并标在试卷的相应位置。听完每段对话后，你都有10秒钟的时间来回答有关小题和阅读下一小题。每段对话仅读一遍。 ( ) 1. ? A. . B. . C. . ( ) 2. ’t ? A. . B. . C. ’t . ( ) 3. ’s ? A. . B. . C. . ( ) 4. ’s ’s ? A. A . B. A . C. A . ( ) 5. ? A. ’t . B. . C. . 第二节（共15小题；每小题1分，满分15分） 听下面5段对话或独白。每段对话或独白后有几个小题，从题中所给的A、B、C三个选项中选出最佳选项，并标在试卷的相应位置。听每段对话或独白前，你将有时间阅读各个小题，每小题5秒钟；听完后，每小题将给出5秒钟的作答时间。每段对话或独白读两遍。 听第6段材料，回答第6至7题。 ( ) 6 ? A. . B. . C. . ( ) 7 ? A. . B. . C. . 听第7段材料，回答第8至10题。 ( ) 8 ? A. A . B. A . C. A . ( ) 9 ? A. a . B. a . C. a . ( ) 10 ? A. . B. . C. . 听第8段材料，回答第11至13题。 ( ) 11 ? A. a . B. a . C. . ( ) 12 ? A. 1 . B. 2 . C. 3 . ( ) 13 ? A. . B. . C. . 听第9段材料，回答第14至17题。
系2004级专业《大学英语》期末考试试卷(B) 楚雄师学院 2004 学年上学期期末考试卷 B 卷课程《大学英语》考试时间： 120 分钟 班级：学号 Section A Directions：In this section, you will hear 10 short conversations. At the end of each conversation, a question will be asked about what was said. Both the conversation and the question will be spoken twice. After each question there will be a pause. During the pause, you must read the four choices marked A), B), C) and D), and decide which is the best answer. Then mark the corresponding letter on the ANSWER SHEET with a single line through the center. Example：You will hear: M: Is it possible for you to work late, Miss Green? W: Work late? I suppose so, if you really think it's necessary. Q：Where do you think this conversation most probably took place? You will read: A) At the office． B) In the waiting room. C) At the airport. D) In a restaurant. From the conversation we know that the two were talking about some work they have to finish in the evening. This is most likely to have taken place at the office．Therefore, A) "At the office" is the best Answer. You should mark A) on the ANSWER SHEET with a single line through the center. 1. A) She's studying for a physics exam. B) She's planning her class schedule. C) She has a degree in astrophysics. D) She plans to graduate this year. 2. A) He already has a job. B) He wi11 probably work at the library. C) He needs to study full time. D) He plans to work at the library in the summer. 3. A) 35 miles per hour.
2005 －2006 学年第二学期 《高级英语》期末考试试卷（A）参考答案 I.Fill in the blanks with the appropriate forms of the given words and phrases. (15%) 1. speaks volumes 2. in the vicinity of 3. at his disposal 4. acted as 5. oblivious 不知道的of 6. look up to 7. to no avail 8. follow suit 9. a battery of 10. in lieu of场所 11. unparalleled 12. reassuring 13. circulation 14. significance 15. engulfed II.Paraphrase the following sentences, especially paying attention to the underlined part. （20%）看要求评分 III.Proofreading (10%) The Great Depression first started in the New York Stork Exchange. In the 1920s, there were fatal flaws on the prosperity 1. in of the economy. Overproduction of crops depresses food prices, 2. depressed and farmers suffered. Industrial workers were earning better wages, but they still did not have enough purchased power to continue buying 3.purchasing the flood of goods that poured out of their factories. With profits soar and interest rates low, a great deal of money was available 4.soaring for investment, and much of tha t capital wen t into reckless 5. but speculation. Billions of dollars \that poured into the stock market, and 6 that frantic bidding boosted the price of share far above their real value. 7.shares As long as the market prospered, speculators could make fortunes overnight, but they could be ruined just as quick if stock 8.quickly prices fell. On October 24, 1929 –“Black Thursday” -- a wave of panic selling of stocks swept the New York Stock Exchange. Once started, the collapse of shares and other security prices could not be halted. By 1932, thousands of banks and over 100,000 businesses had been failed. Industrial 9. been production was cut in half, farm income had fallen by more than half, wages had increased 60%, new investment was 10. decreased down 90%, and one out of every four was unemployed in the USA. IV．Reading comprehension (25%) 1-5 BCADB 6-10 BCBCA 11-15 CCBCA 16-20 DDCCB 21-25 BAACA V. Text analysis (30%) 看要求评分。
01 Passage 1 Hypnotism (催眠术) is very old. Thousands of years ago people started to use it in Egypt. The use of hypnotism has grown very much since that time. Today, doctors and scientists are in almost every country hypnotize people to help them with their problems. What is hypnotism, and how does it work? Many people think that a hypnotist puts people to sleep. Then he makes the hypnotized people do strange things. This is not what a hypnotist does. Hypnotism is really just a way to relax the mind and body. What are some of the uses of hypnotism? We go to a hypnotist because w e have a problem. The problem makes us unhappy. The hypnotist asks us to think hard about something and relax. When we are relaxed, t he hypnotist gives us some ideas to help us with our problems. Hypnotism can help people to remember things. The police sometimes ask hypnotists to help them. For example, a man sees an accident. He forgets the license number of the car he sees. If he is hypnotized he may remember it. The police can then find the car and catch the driver. People who are hypnotized can also make mistakes or say something that isn't true. People remember what they think they saw. That may not be what really happened. The police don't hypnotize people who do something wrong. Why not? People who are hypnotized may say something that isn't true. A person who has done something bad has a good reason to say something that isn't true. 1. Hypnotist helps people by ____. [A] putting them to sleep [B] helping them to get relaxed [C] offering his ideas about their problems [D] making them forget their problems 2. When hypnotized, some people may say something that is not true, because ____. [A] they do not remember what has happened [B] they remember what they think has happened [C] they do not know what has happened [D] they are not interested in what has happened 3. According to the passage, which of the following is TRUE?____ [A] Hypnotism is very different form what it used to be. [B] When a person is hypnotized, his body gets relaxed, while his mind works hard. [C] Hypnotism is much more widely used today than it was thousands of years ago. [D] When hypnotized, a person will do something strange. 4. The passage mainly talks about ____. [A] how hypnotism works [B] the development of hypnotism [C] the use of hypnotism [D] the wonder of hypnotism
学号 姓 系部 专业 班级 考试科目 考试时间 年 月 日 密 封 山东师范大学历山学院201３—2014学年第二学期 期末考试试题(B 卷) 试题卷 (时间12０分钟,满分10０分) 课程编号: 课程名称: 大学英语 适用年级: ２01３级 适用专业: 非英语 学制: 三 注意:１、本试题试题卷共六页。 2、本试题所有答案应写在答案卷上,否则不予计成绩。 Ⅰ ⅠListe ｎing pr ｅhens ｉｏn (1５％) Sectio ｎ Ａ D ｉｒe ｃtions: In ｔhi ｓ s ｅct ｉon ｙo ｕ ｗill ｈear 10 short dial ｏgue ｓ。 At t ｈe e ｎｄ of e ａc ｈ ｄi ａlog ｕe, a q ｕｅstion ｗｉll b ｅ asked abou ｔ w ｈa ｔ was said 、 Ｂｏth the dialo ｇues and questio ｎｓ will be spo ｋｅn tw ｉce 。 After ea ｃh q ｕest ｉon th ｅre w ｉll b ｅ a pause 。 Ｄuring the p ａu ｓe, yo ｕ must read th ｅ ４ choices marke ｄ A,B,C an ｄ D,ａnd dec ｉde w ｈich is the bes ｔ answ ｅｒ。 Then write the corresp ｏndi ｎg letter ｏn the A ｎｓwer Ｓheet 。 １。 Wher ｅ did thi ｓ c ｏnversatio ｎ p ｒo ｂa ｂl ｙ ｈappen ？ A In a d ｒu ｇ st ｏr ｅ、 Ｂ I ｎ ａ sh ｏｐ、 C In a ｓupermarke ｔ。 Ｄ In a ｒｅｓｔaurant. 2、 When wi ｌl ｔh ｅ t ｒａin leave? A １4:２0 Ｂ １４:00 Ｃ 14:40 D 14:30 3。 How m ａｎy ｐeople ar ｅ th ｅre in the m ａn ’s f ａmily ？ ?A 5。 B ４、 C 3、 D 6、 4. Ho ｗ i ｓ ｔｈａｔ school? A It ＇s even ｗo ｒs ｅ th ａn peop ｌｅ say 、 B It's bet ｔer than it used t ｏ be 。 ? C It’s b ｅtte ｒ t ｈan people sa ｙ、 D I ｔ’ｓ not a ｓ g ｏo ｄ as it w ａs 。 5。 What is imp ｌi ｅd in t ｈe co ｎversatio ｎ？ Ａ T ｈe ｃhildren w ｅr ｅ ｅｎjoyin ｇ t ｈemselve ｓ、 ? B T ｈe ch ｉldren d ｉd ｎ＇t e to th ｅ ｐar ｔy 。 ? C Ｔhe childr ｅn were ｇｉving ａ l ｏt of ｆu ｎ ｉｎ th ｅ party. Ｄ The chi ｌｄｒen wer ｅ n ｏｔ ｂe ｈa ｖi ｎg th ｅmselves ｉn ｔh ｅ party 。 6. Wha ｔ will ｔhe ｗｅathe ｒ be l ｉke ？ A Ｉt ｗｉll ｇet be ｔｔer Ｂ Ｒａiny C Ｓｕnny 、 D It ｉs ｃolder. ７。 Ｗｈat does th ｅ ｗｏman mean ？ A Sh ｅ doe ｓ not agree ｗit ｈ the ｍan 。 B She ｄｏes ｎo ｔ know what
滨州学院2007－2008学年第一学期期末考试 英语专业（本）2005级《高级英语》试卷（B） （答案一律写在答题纸上，在本试卷上做答无效） I. Multiple Choice: (30%) Section 1: Choose the word or phrase that is closest in meaning to the underlined part (20%). 1. The US launched military attacks on Iraq for the purpose of establishing its possession of weapons of mass destruction. A setting up B building C constructing D ascertaining 2. Artificial diamond is indistinguishable from genuine one, but much cheaper. A differential in B indifferent to C differentiable from D identical to 3. I was offered my teaching job back but I declined. Later I became a geologist for an oil company. A received B accepted C hesitated D refused 4. The glaring of the sun makes all stars invisible. A coldness B darkness C brightness D hotness 5. Tony became disdainful of his friends when he succeeded in the attempt. A scornful B proud C thankful D grateful 6. Motors and bicycles threaded their way among the throngs of people entering and leaving the market. A swarm B crowds C flock D herd 7. Police followed the would-be thieves and caught them red-handed. A enraged B likely C attempted D timid 8. The news was such a shock that it still hasn’t really sunk in yet. A collapsed B been comprehended C been soaked D been leaked 9. Shakespeare was one of the most prolific writers in England. A creative B productive C ingenious D inventive 10. The hypothesis proposed for the origin of the solar system was to be discussed this week. A protected B provoked C stated D approved 11. The buildings collapsed in the earthquake. A broke down B turned down C put down D kept down 12. Tom’s answer was equivocal whenever the teacher asked the same question of him. A identical B different C ambiguous D difficult 13. There were incessant demands for the resignation of the Georgian president from the office for his inefficient running of state affairs.
Final Test for English Majors of 2002 (Advanced English) I. Choose the best answer: 25% 1. She gave thanks for our contribution. A. procure B. profuse C. profound D. prodigious 2. and conspiracy will not succeed; the government will not be defeated. A. Subscription B. Subsidence C. Submission D. Subversion 3. A good friend will not desert one in time of . A. adversary B. adverse C. adversity D. advent 4. The psychiatrist gave that the man was insane at that time. A. evidence B. argument C. witness D. testimony 5. She is a woman of erect and handsome . A. carriage B. figure C. personage D. appearance 6. His with everything we suggest makes it hard to know what he really feels. A. alliance B. compliment C. compliance D. compassion 7. Diligent police work will help crime. A. endorse B. eradicate C. fluctuate D. radiate 8. Nutritionists food into seven basic groups. A. categorize B. clarify C. ratify D. separate 9. Only states are able to make treaties. A. sovereignty B. sovereign C. democratic D. democracy 10. diseases may be spread by viruses and bacteria. A. Deadly B. Mortal C. Fatal D. Infectious 11. His only is an occasional game of golf. A. diversification B. diversion C. diversity D. divergence 12. One of California?s most problems is an inadequate water supply. A. acute B. unusual C. persistent D. unexpected 13. Large areas of Alaskan land remain due to harsh climate. A. inaccessible B. immature C. desolate D. parched 14. Constant interruption of his work him. A. threshed B. tormented C. exasperated D. evaporated
新编大学英语A2期末考试试卷 Part I Listening Comprehension(20%) Section A Directions: In this section, you will hear 10 short conversations. At the end of each conversation, a question will be asked about what was said. Both the conversation and the question will be spoken only once. After each question there will be a pause. During the pause, you must read the four choices marked A), B), C) and D), and decide which is the best answer. Then mark the corresponding letter on the Answer Sheet with a single line through the center. Section A. 1. A. An advertisement B. A newspaper C. Their work D. A dream 2. A. On foot B. By car C. By bus D. By bike 3. A. Three B. Four C. Five D. Six 4. A. The restaurant provides good food B. She enjoys her part-time job C. The restaurant offers cheap food D. There are several cooks in the restaurant. 5. A. The movie was disappointing B. The movie was expensive to see. C. He wants to see the movie again. D. He should have seen the movie at home. 6. A. $ 64 B.$ 86 C. $96 D. $140 7. A. To stay at home B. To go to bed immediately C. To see a movie D. To go to a party. 8. A. Tom is unable to hear well. B. Tom didn’t say anything at the meeting. C. Tom doesn’t listen to him. D. Tom went out before the meeting was over.
高级英语期末考试试题 选择题部分 本试卷共8页，满分100分；考试时间150分钟，全部题目用英文作答（英译汉题目外），并将答案写在答题纸的相应位置上，否则不计分。 I. Each of the following sentences is given four choices of words or expressions. Choose the right one to complete the sentence and blacken the corresponding letter on your Answer Sheet. (15 points, 1 point for each) 1. With his last ______ , he murmured the name of the person who murdered him. A. gasp B. choke C. exhale D. respiration 2. The teenager’s ______ of the pop star worried her parents. A. applause B. compliment C. adulation D. recommendation 3. The adventurous mission ______ his spirits. A. exalted B. inspired C. gladdened D. exhilarated 4. The girl made one last ______ to her father for permission to go to the party. A. appeal B. pray C. suggestion D. attraction
《综合英语》考试试卷（A卷、闭卷） Part I Reading Comprehension (阅读理解) （每小题3分，共15分） Passage One Suppose we built a robot to explore the planet Mars. We provide the robot with seeing detectors to keep it away from danger. It is powered entirely by the sun. Should we program the robot to be equally active at all times? No. The robot would be using up energy at a time when it was not receiving any. So we would probably program it to cease its activity at night and to wake up at dawn the next morning. According to the evolutionary theory of sleep, evolution equipped us with a regular pattern of sleeping and waking for the same reason. The theory does not deny that sleep provides some important restorative functions. It merely says that evolution has programmed us to perform those functions at a time when activity would be inefficient and possibly dangerous. However, sleep protects us only from the sort of trouble we might walk into; it does not protect us from trouble that comes looking for us. So we sleep well when we are in a familiar, safe place, but we sleep lightly, if at all, when we fear that bears will nose into the tent. The evolutionary theory accounts well for differences in sleep among creatures. Why do cats, for instance, sleep so much, while horses sleep so little? Surely cats do not need five times as much repair and restoration as horses do. But cats can afford to have long periods of inactivity because they spend little time eating and are unlikely to be attacked while they sleep. Horses must spend almost all their waking hours eating, because what they eat is very low in energy value. Moreover, they cannot afford to sleep too long or too deeply, because their survival depends on their ability to run away from attackers. 1.The author uses the example of the robot in space exploration to tell us . A) the differences between robots and men B) the reason why men need to sleep C) about the need for robots to save power D) about the danger of men working at night 2.Evolution has programmed man to sleep at night chiefly to help